(a) Field of the Invention
The present invention relates to a navigation system. More specifically, the present invention relates to a navigation system that is installed in an automobile and provides information on a current location of the automobile, as well as other supplementary information.
(b) Description of the Related Art
A navigation system receives waves from a plurality of wave sources, that is, satellites, and obtains a measure of the distance from the wave sources using time differences between the arrival of the waves, differences of phase, and Doppler shift so that the current position of the navigation system is found. If a driver inputs a destination to the navigation system before the automobile starts moving, the current position is displayed on a navigation system map, and the system indicates when to change direction in order to reach the destination.
Some recent navigation systems are also equipped with a voice guidance function. This function guides the driver to proceed down branch roads, and announces this guidance several times until the car reaches the appropriate branch road. Examples of this guidance are "Please turn to your right after driving one kilometer." or "Please turn to your right after driving 700 meters."
When the above noted announcements are played, the output from the automobile sound system is muted, and when the announcements are finished, the output is resumed. Because of the potential inconvenience of this audio cutout, the driver should have the opportunity to disable this function.